mudbuddha

Patrick- I run Wossner pistons. They are also swain (?) coated also to help combat high temp.

JET951

Not the first time we installed the ARP's on your car. We used the ARP recommended torque and the head gasket still failed within that 7-10 track days. That is why on the next HG instal we went to the 100ft lbs. Im not sure how many track days you did after that.

Its quite possible that you are correct, One of our tracks is 2 1/2 hours away. In the past 7 years i have been towed home twice. At close to $600 for the tow its not fun. Not to mention the strange towies

Yes, Stock head studs and torque.

I agree they look good, but no real specific data there about why we see the wear we are seeing. Unless we try a set of ARP or even the larger Heritage studs we wont know if the wear to the cometic is a clamping issue

Sean

blown 944

So are you gonna answer my ?..???

When are you gonna get some trap speeds out of that beast?

JET951

Sorry Sid,
Missed that one. hopefully soon, western sydney international drag way have wednesday night drags. It only cost $50 or so and you get about 5 runs if you get there by 3. Its quite a long wait but you get to check out the other cars in the line ups.

333pg333

Just don't tell Bruce..heheheh...

Yes, that's right on the torquing. When we went to the higher tq rate we got a better longevity.

refresh951

Sean - What you have accomplished with these cars is amazing and inspiring. Thanks for sharing your projects here. I have read everyone of your threads.

According to Cometic, this kind of damage is the result of head lift/flex that overworks the seal boss and then a fatigue fracture occurs and starts to propagate. Some refer to this a "chomping". I think the math will show that head/block flex is the greatest at cylinders 2 and 3. I do think that ARP studs and higher torque will help some but that much of what occurs is the result of high peak cylinder pressure (22psi) and the large bore size in our motors. I have been researching this extensively for my own build. Fatigue failure is fairly repeatable and thus the consistency you have experienced.

Also, I believe in general that HG failures on cylinder 4 are more related to detonation (4 getting the least cooling) rather than flex. Obviously detonation has not been an issue for your car with relatively low CR and E85.

333pg333

Shawn I’d assume that we’d see consistent peppering on #4 if that were the case? Not sure that we’ve seen any overt signs of detonation? How about you guys?
I think Sean’s new build with the 3L block and Siamesed bores has to be better in this regard. The possible loss of cooling is a secondary matter. I am hoping the line bored, pinned girdle and deckplated block will help me in these h/g matters. Sean is opening that motor up next week for a new h/g just as a precaution and perhaps the main bearings before it will finally go back into the car. I shall report back findings on this motor.
Overall, it’s great to see some of us are working away at this achilles heel of our cars.

refresh951

I am certainly not an expert in these areas. I have been researching this and looking at trends under various conditions. I see understanding this as key to my own builds success. Not exactly sure what you mean by this:

"Shawn I’d assume that we’d see consistent peppering on #4 if that were the case?" Have most of the failures you have seen with E85 been on cylinder 4?

blown 944

I havnt seen any sign of detonation. I think we are also experiencing a problem with the studs being so far from the bores.

I have had better luck with filling the block, however, I pulled the head 3/4 through the season last year and saw the thin gasket on the bottom side starting to split. Mine was dead center of the bore. Right where the gasket is embossed.

I am going to see if cometic will do a gasket for me without the embossing. Or see if I could get away with deleting the lower thin gasket and just copper spray the thick one.

Any way you look at it, for the horsepower and how many miles I put on it, I think it was great.

Dave Novak will be showing something completely different soon. I am looking forward to this!! If it works out well I could see a huge increase in boost pressure.

refresh951

I completely agree Sid. I would gladly change out the gasket occasionally to have the success Sean has had.

What cylinder did you get the fracture on?

333pg333

'Peppering' might be Aussie slang for the detonation marks on top of the piston?

I like the idea of that gasket if you can get it made Sid.

Is Dave proposing something gasket-wise or a totally new way of buttoning up the system overall?

blown 944

It was at the top of #1 cylinder

I think they'll make it for me. I've spoken with them and I just had a 104mm gasket done for no addnl charge.

Dave is trying something completely different.

refresh951

Thanks! A 104mm? What have you got going on? I am looking forward to seeing whatever it is. I am sure it will once again be pushing the envelope.

blown 944

Just getting the gasket a little further out from the cylinder. As you know, the 103mm is very close to protruding into the cylinder. Just a boring mod.

333pg333

Interestingly Sean was mentioning the 'embossing' on the normal Cometics. Keep us in the loop should you succeed in getting them to make some.